The centennial of World War I — which commenced in 2014 and continues through 2018 — has stimulated a biblical flood of commemorative exhibits and events, and new works on the conflict are certain to flow relentlessly during the coming years. Testament of Youth, however, has already established a high-water mark that latecomers will find difficult to surpass. Based on Vera Brittain's 1933 memoir, the film chronicles the devastating effects of the war on a tight circle of friends, a small but dismayingly representative sample that effectively stands in for the vast millions maimed and killed.

When we first meet Vera (Alicia Vikander), she's plowing determinedly through a joyous crowd celebrating the November 1918 armistice, but her grim-faced, hollow-eyed demeanor makes it immediately clear that the cessation of fighting doesn't truly mark the end of the war — she carries the experience inside her, and it promises to remain permanently resident. After that swift, disorienting prologue, which communicates with a telegraphic urgency, a title card announces "Four years earlier," and an altogether different Vera manifests onscreen, a youthful beauty swimming in sun-dappled waters near her home. Brother Edward (Taron Egerton) and his school chum Victor (Colin Morgan) soon appear on the bank but, fearful of rats, hesitate to dive in until Vera's bold example shames them into joining her. Vera's willful independence is further emphasized when the trio returns to the family house, where a surprise gift — a piano — awaits. Far from pleased, an aggrieved Vera berates her parents (Dominic West and Emily Watson) for wasting money that could have instead paid for her tuition to Oxford, which she longs to attend. The traditionalist Mr. Brittain resists that outlandish notion and wants Vera to win a suitor with her facility at the keyboards, but his freethinking daughter prefers a university education and a literary career.

Miraculously, the dreams of both father and daughter appear on the verge of fulfillment when Vera wins entrance to Oxford's Somerville College and becomes romantically entangled with another of Edward's friends, Roland (Game of Thrones heartthrob Kit Harington), but the Great War's arrival forces the abandonment of all such hopes. Roland, Edward, and Victor successively march off to the front, fresh meat for the war's ceaseless grinder, and Vera refuses to sit idly by as others sacrifice: She leaves her studies to become a volunteer nurse, first in England and then in France, where she tends not only the allied wounded but also German soldiers. Brief sunshine — temporary respite, fleeting happiness — occasionally interrupts the overall gloom, but the numbing frequency of death drains the once-radiant Vera of energy, until she finally becomes the spent, despairing woman of shadow seen in the film's opening sequence. Only when she stumbles into a postwar debate over German reparations does Vera's fire again flare to vibrant life, and she finds her new calling as an impassioned voice for pacifism.

We've seen all of this before, of course: The particularly grim, traumatic nature of World War I has been a staple of cinema since the silent era — Abel Gance's J'accuse (1919) was partially shot during war's final months and featured actual battle footage — and any number of compelling films (All Quiet on the Western Front, Paths of Glory, Gallipoli) have used the conflict to make persuasive antiwar statements. But Testament of Youth has a raw immediacy that blows the dust from what some might consider distant history. Although this is his first theatrical feature, director James Kent has a long TV career that includes several documentaries, and he makes smart, canny use of intimate close-ups and vérité-like hand-held shots to bridge the gulf between then and now: There's none of the trapped-in-amber fustiness of so many period dramas.

What most distinguishes the film, however, is the performance of Vikander. Impressive as she was in Ex Machina, the Swedish actress is altogether extraordinary here, speaking in a flawless English accent and offering a nuanced, entirely believable portrait of a proto-feminist who's alternately vulnerable and fierce, as self-sacrificing as she is self-reliant. Although the film's title refers primarily to the lost promise of the young soldiers it mourns, it's equally a testament to the talents of two astonishing women: Vera Brittain and Alicia Vikander.